This invention relates generally to a method and apparatus for calibrating digital electric energy consumption meters after manufacture but before installation in order to insure that the meters are operating accurately. More particularly, this invention is an improved method and apparatus for calibrating digital electric energy consumption meters of the type described in my U.S. Pat. No. 5,061,890 which issued on Oct. 29, 1991 and as further described in my copending patent application Ser. No. 07/766,136 which was filed on Sep. 27, 1991. The patent specification is incorporated herein by reference.
All electric energy consumption meters, be they digital or analog, must be calibrated prior to installation to be certain that they are operating accurately. The conventional analog meters which are presently in use generally require several minutes to calibrate prior to packing and shipping. I have discovered a unique method and apparatus for calibrating the digital electric energy consumption meters described in my aforementioned patent disclosures which may be accomplished in a matter of a few seconds or less as opposed to a few minutes.
My aforementioned patent disclosures disclose a digital electric energy consumption meter which performs voltage and current sampling in timed cycle clusters. Readings of voltage and current need not be simultaneous and also if desired the actual measurement of current need not be taken directly from the power source at prevalent voltage potentials and therefore less expensive hardware is required and also very low computing power is required since relatively few readings are necessary for acceptable accuracy. All of this is described in greater detail in both of the above-identified patent disclosures.
My above-described digital electric energy consumption or watt hour meter performs algorithmic analysis on these voltage and current samplings to determine the electrical energy being sampled through the use of a computer which includes a microprocessor, appropriate memory, and a clock for timing and initiation of sampling. The algorithmic analysis performed on the current and voltage samplings is preferably Fourier Series based. I have discovered a very unique method and apparatus for calibrating this meter which varies significantly from the calibration techniques for the old revolving disk analog meters and other digital meters.